MassDOT discharge outlets and fill points are marked by __ placards.

The correct placard color for MassDOT discharge outlets and fill points is red. This designation is in place to enhance visibility and immediate recognition, ensuring that emergency responders and personnel can quickly identify these critical locations. The red color often indicates caution and signifies that these points may be associated with hazardous materials or important operational functions within the transportation infrastructure. Red is widely recognized in various safety standards as a color for alerting individuals to potential danger or important information related to safety and emergency services.

In contrast, the other colors typically indicate different meanings in safety or visibility contexts and are not used for these specific discharge outlets and fill points as designated by MassDOT standards.